Reaction of CO with Preadsorbed Oxygen on Low-Index Copper Surfaces: An Ambient Pressure X-ray Photoelectron Spectroscopy and Scanning Tunneling Microscopy Study

Abstract

The reaction of CO with chemisorbed oxygen on three low-index faces of copper was studied using ambient pressure X-ray photoelectron spectroscopy (XPS) and high-pressure scanning tunneling microscopy. At room temperature, the chemisorbed oxide can be removed by reaction with gas-phase CO in the 0.01−0.20 Torr pressure range. The reaction rates were determined by measuring the XPS peak intensities of O and CO as a function of time, pressure, and temperature. On Cu(111) the rate was found to be one order of magnitude faster than that on Cu(100) and two orders of magnitude faster than that on Cu(110). The apparent activation energies for CO oxidation were measured as 0.24 eV for O/Cu(111), 0.29 eV for O/ Cu(100), and 0.51 eV for O/Cu(110) in the temperature range between 298 and 473 K. These energies are correlated to the oxygen binding energies on each surface.

Catalytic Intermediates of CO2 Hydrogenation on Cu(111) Probed by In Operando Near‐Ambient Pressure Technique

“…The peak located at about 292.7 eV corresponds to the photoelectron emissionf rom gas-phase CO 2 .The interpretation of the C1ss pectrum facilitated the analysiso ft he O1sc ounterpart and also accounted for the different relative abundances. [30,32] The appearance of oxidized carbon structures was further supported by UPS measurement (Figure 3b). [31,48] The component at 531.4 eV was attributed to the CO 2 dÀ and/or HCOO À groups,o nt he basis of literature data that reported similar peak positions in the O1ss pectrum [47,48] (Table 1).…”

“…Figure 1d shows the O1s and C1ss pectra in 0.4 mbar CO 2 at room temperature with extended exposure time. [31,32] We further manifested that the build up of atomico xygen could hinder CO 2 activation owing to the reduction of the active Cu surface (see the Supporting Information for detailed analysis). [29,30] The CO 2 dÀ that resulted from nondissociative adsorption of CO 2 was also detected at 531.4 eV (O 1s) and 288.4 eV (C 1s).…”

Catalyst Chemical State during CO Oxidation Reaction on Cu(111) Studied with Ambient-Pressure X-ray Photoelectron Spectroscopy and Near Edge X-ray Adsorption Fine Structure Spectroscopy

“…7,23,24 In addition to the chemisorbed layer, a new peak grows with increasing exposure to O 2 at 530.2 eV, which we assign to formation of Cu 2 O. They all produce XPS peaks at lower binding energies.…”

“…7 The reaction intermediate (CO 2 δ-) was reported in the literature to produce O and C peaks at 531.4 eV and 288.4 eV on metallic Cu, 26,28 however there is a lack of data on the CO 2 δand CO peak energies on Cu 2 O. The peaks at around 531.5 eV and 286.1 eV arise from CO adsorbed on metallic Cu(111).…”

“…7 The last two data points in the dashed box are taken respectively after O 2 is pumped out (with CO remaining in the chamber), and after CO is pumped out. The peak intensity ratios are calibrated using intensity ratios of samples with known coverages.…”